Flexible display

Abstract

A flexible display is disclosed. The flexible display including an oxide semiconductor thin film transistor on a plastic substrate includes a first buffer layer disposed on the plastic substrate, a second buffer layer disposed on the first buffer layer and formed of silicon oxide (SiOx), and an active layer disposed on the second buffer layer and formed of an oxide semiconductor. The first buffer layer includes a lower layer directly contacting the plastic substrate and formed of silicon nitride (SiNx) and an upper layer disposed on the lower layer and formed of silicon oxide (SiOx).

What is claimed is: 
     
       1. A flexible display device comprising an oxide semiconductor thin film transistor on a flexible substrate, comprising:
 a first buffer layer disposed on the flexible substrate; 
 a second buffer layer disposed on the first buffer layer and formed of silicon oxide (SiO x ); and 
 an active layer disposed on the second buffer layer and formed of an oxide semiconductor, 
 wherein the first buffer layer comprises: 
 a lower layer directly contacting the flexible substrate and formed of silicon nitride (SiN x ); and 
 an upper layer disposed on the lower layer and formed of silicon oxide (SiO x ), 
 wherein the lower layer comprises a first lower layer and a second lower layer disposed on the first lower layer, and 
 wherein the first and second lower layers respectively include first and second micro size pores that are separated from each other. 
 
     
     
       2. The flexible display of  claim 1 , wherein the lower layer has a thickness equal to or greater than that of the upper layer. 
     
     
       3. The flexible display of  claim 1 , wherein the first and second lower layer are formed through a separate process. 
     
     
       4. The flexible display of  claim 3 , wherein the first and second lower layers have substantially the same thickness. 
     
     
       5. The flexible display of  claim 4 , wherein the first and second lower layers have a thickness between 100Å to 3,000Å. 
     
     
       6. The flexible display of  claim 1 , further comprising a light shielding layer disposed between the first buffer layer and the second buffer layer and overlapping the active layer. 
     
     
       7. A flexible display device comprising an oxide semiconductor thin film transistor on a flexible substrate, comprising:
 a first buffer layer disposed on the flexible substrate; 
 a second buffer layer disposed on the first buffer layer and formed of silicon oxide (SiO x ); and 
 an active layer disposed on the second buffer layer and formed of an oxide semiconductor, 
 wherein the first buffer layer comprises: 
 a lower layer directly contacting the flexible substrate and formed of silicon nitride (SiN x ); and 
 an upper layer disposed on the lower layer and formed of silicon oxide (SiO x ), 
 wherein the lower layer comprises a first lower layer and a second lower layer disposed on the first lower layer, and 
 wherein the first lower layer has a density higher density than that of the second lower layer. 
 
     
     
       8. The flexible display device of  claim 7 , wherein the first lower layer has a density higher density than that of the second lower layer. 
     
     
       9. A display device on a flexible substrate, comprising:
 a first lower buffer layer disposed on the flexible substrate; 
 a first upper buffer layer disposed on the first lower buffer layer, wherein the first lower buffer layer and the first upper buffer layer are formed of a different insulation material; 
 a light shielding layer disposed on the first upper buffer layer; 
 a second buffer layer disposed on the first upper buffer layer including the light shielding layer, wherein the second buffer layer and the first upper buffer layer are formed of the same material; and 
 an active layer disposed on the second buffer layer and formed of an oxide semiconductor and vertically overlapping the light shielding layer. 
 
     
     
       10. The display device of  claim 9 , wherein the second buffer layer electrically insulates the light shielding layer from the active layer. 
     
     
       11. The display device of  claim 9 , wherein the light shielding layer protects the active layer from external light. 
     
     
       12. The display device of  claim 9 , wherein the first lower buffer layer includes first and second insulation parts that are formed of the same insulation material and formed through a different process. 
     
     
       13. The display device of  claim 12 , wherein the first and second insulation parts are formed of silicon nitride. 
     
     
       14. The display device of  claim 12 , wherein the second buffer layer and the first upper buffer layer are formed of silicon oxide. 
     
     
       15. The display device of  claim 12 , wherein the first and second insulation parts have substantially the same thickness. 
     
     
       16. The display device of  claim 15 , wherein the first and have second insulation parts have a thickness between 100Å to 3,000Å. 
     
     
       17. The display device of  claim 12 , wherein the first and have second insulation parts respectively include first and second micro size pores that are separated from each other. 
     
     
       18. The display device of  claim 12 , wherein the first insulation part has a density higher than that of the second insulation part. 
     
     
       19. The display device of  claim 9 , wherein the device has a thin film transistor with a threshold voltage shifted by −0.03 V. 
     
     
       20. The display device of  claim 19 , wherein the threshold voltage has a degree of scattering in Δ0.72.